The present invention relates to an intake device for an internal combustion engine, in which an additional closing element for dividing off an accumulator passage is provided in the intake passage.
The use of closing or sealing elements for the intake passages of internal combustion engines is generally known. In internal combustion engines, the achievement of impulse charging results in subjection of flap valves to severely demanding conditions. Impulse charging requires use of rapidly switching flap valves to achieve short switching times. To satisfy requirements established by thermodynamic calculations, switching times of 2 ms should be achieved in such cases.
The short switching times for impulse charging of internal combustion engines are necessary since the switching behavior of the flap must be adjusted to the supercharging process for the cylinder, which is a direct function of the valve opening times of the intake valve of the cylinder. Impulse charging is understood as a method in which the intake passage is temporarily sealed using a flap upstream of the intake valve of the cylinder, so that a partial vacuum results downstream of the flap during the intake stroke of the cylinder when the intake valve is open. If the flap is opened with a partial vacuum existing, the partial vacuum accelerates the released charging column of intake air behind the flap, as a result of which this air flows into the cylinder with a high impulse and causes greater filling of the combustion chamber. This method is described, for example, in Kreuter, U.S. Pat. No. 6,422,184 (=DE 199 08 435).
In order to implement this method, U.S. Pat. No. 6,422,184 describes a flap mechanism which is biased in the closing direction, whereby closure of the flap may be effected with the aid of an electromagnet. The flap is opened as a result of the partial vacuum which arises between the flap and the intake valve, in the region of the intake passage which is referred to as the accumulator passage.
To achieve the fast switching times described, however, a large expenditure for components is necessary. In particular, the closing of the closing element in the short time required causes problems, since the switching must be performed against the flow occurring in the intake tract.
However, the switching speed during closing is also of great importance, since in this way overpressure is to be generated in the passage section between the element and the intake valve. This overpressure is used for so-called residual exhaust gas purging in the cylinder upon opening of the intake valve, by which the exhaust gas residues may be completely removed from the combustion chamber before the outlet valve closes again.